harry reid say there's was a huge explosion. >> we don't know exactly what happened but it was a violent explosion, we know that. my thoughts are with those who are injured and, of course, families of those with lost loved ones. >> want to bring in our pentagon correspondent, barbara starr. tell us, first of all, what do we know about how this even happened? >> reporter: well, suzanne, the military is saying seven marines were killed when a 60 millimeter mortar shell, already in the tube, in the weapon essentially exploded. seven marines killed, a number injured and medevac'd to hospital. likely with serious trauma injuries about the training situation, they would have been standing quite close to the mortar and to the weapon when it exploded. now a major investigation, of course, under way trying to determine what exactly happened and trying to see how they go forward from here. but seven military families, suzanne, getting the worst possible news today. >> such a shame. thank you, barbara. appreciate that. >>> a plan now to commit mass murder on a college campus. police in orlando, flo